So I got a Switch with this issue but that’s not how the problem started. The Switch would boot with a good battery but the battery would not charge even though when I plugged the USB-C cable in, the charging icon would come on but no amps drawn. It would also boot if I plug The USB-C cable in. I did not find any shorts in the usual places. Everything checked out fine. So I decide to replace the M9 and I was getting the usual amps on both sides of the USB-C port with the new M9. I put much of it back together and I plugged in the USB-C Cable and it showed the Battery charging icon… then the screen went black. I got nothing. I unplugged the battery and plugged it back in. I press the power Button and I got the Nintendo logo and then nothing. I have replace The M9, BQ and Fuel Gage IC many times and I am still getting the same results. I did try the above suggest to remove the USB-C Port. I did that and still the same results. I am scratching my head on what the issue is. Could it be EMMC NAND failure?
Try to reflow Tegra SoC and RAMs